Compact wide field of view digital camera with stray light impact suppression

ABSTRACT

A point action camera or other compact digital camera having a wide field of view, includes an optical assembly that includes multiple lens elements, including at least one lens element that has an aspheric lens surface. The optical assembly is configured to provide a field of view in excess of 120 degrees. The digital camera is configured such that not less than 90% of return ghosts foci are more than +/−2 mm from the image sensor plane.

PRIORITY AND RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.62/075,161, filed Nov. 4, 2014. This application is also acontinuation-in-part (CIP) which claims priority to U.S. Ser. No.14/810,377, filed Jul. 27, 2015, now U.S. Pat. No. 9,726,859, which is aCIP of U.S. Ser. No. 14/215,056, filed Mar. 16, 2014, now U.S. Pat. No.9,091,843. This application is also related to U.S. Ser. No. 14/215,041,filed Mar. 16, 2014, now U.S. Pat. No. 9,494,772 and to U.S. Ser. No.14/215,049, filed Mar. 16, 2014, now U.S. Pat. No. 9,316,820, and toU.S. Ser. No. 14/215,058, filed Mar. 16, 2014, now U.S. Pat. No.9,316,808. This application is also one of a group of related,contemporaneously filed patent applications, entitled OPTICAL ASSEMBLYFOR A COMPACT WIDE FIELD OF VIEW DIGITAL CAMERA WITH HIGH MTF, Ser. No.14/932,593; OPTICAL ASSEMBLY FOR A COMPACT WIDE FIELD OF VIEW DIGITALCAMERA WITH LOW LATERAL CHROMATIC ABERRATION, Ser. No. 14/932,663;OPTICAL ASSEMBLY FOR A COMPACT WIDE FIELD OF VIEW DIGITAL CAMERA WITHLOW FIRST LENS DIAMETER TO IMAGE DIAGONAL RATIO, Ser. No. 14/932,717;and A COMPACT WIDE FIELD OF VIEW DIGITAL CAMERA WITH STRAY LIGHT IMPACTSUPPRESSION, Ser. No. 14/932,748. Each of these priority and relatedapplications is incorporated by reference.

BACKGROUND

Point Action cameras, as they are referred to herein, go by many othernames, including point of view cameras (see, e.g.,pointofviewcameras.com), helmet cameras, action cams or action cameras,point of view shooter cams, video action cameras, and extreme sportscameras among others. Brand names include GoPro and ReplayXD.Conventional point action cameras typically have significant distortion,particularly at the outer several degrees of the field of view. Inaddition, astigmatism errors in conventional point action cameras cannegatively impact the appearance of the video images that it captures.It is desired to have a point action camera or other compact digitalcamera that is capable of capturing a wide field of view, or a field ofview that is greater than 90 degrees in either or both of the horizontal(x) and/or vertical (y) dimensions (or an arbitrary axis normal to thedepth (z) dimension), and perhaps 135-150 degrees or more in thehorizontal (x) dimension and/or perhaps 110-120 degrees or more in thevertical (y) dimension, and that is configured with built-in distortionand astigmatism correction.

Distortion in wide field of view cameras has been reduced with imageprocessing software (see, e.g., U.S. Pat. Nos. 8,493,459 and 8,493,460,and US published patent applications nos. US20110216156 andUS20110216157). It is desired however to alternatively provide a pointaction camera or other compact wide field of view digital camera,wherein the distortion that is typically inherent in wide field of viewsystems such as conventional point action cameras is compensated by aneffective and efficient optical design.

Alex Ning describes a six lens design in U.S. Pat. No. 7,023,628 thathas a ratio of total track length (TTL) to effective focal length (EFL),or TTL/EFL, that has a maximum value of 15 over which Ning states thatthe design would not have been considered compact. The Ning six lensdesign also has a minimum value of 8 under which Ning states that thedesign would not achieve the required fish eye field of view. U.S. Pat.No. 7,929,221 describes multiple optical assemblies that each includethree aspheric surfaces on two lens elements and that each have aTTL/EFL ratio between 15 and 25. In an unrelated technical field, U.S.Pat. No. 7,675,694 nonetheless describes multiple optical assembliesthat each include six aspheric surfaces on three lens elements. At U.S.Pat. No. 8,873,167, Ning describes an optical system that includes threelens elements in the first group and either having no aspheric lenselements or two aspheric lens elements, one in each of the two opticalgroups. In one example, Ning discloses a TTL/EPL ratio of 17.6, while inmore compact examples TTL/EFL is described as being not less than 8.

It is also desired to have a compact camera design that capturesreliably focused images. It is therefore desired to have an opticaldesign that features a depth of focus that is greater than 20 microns.

It is recognized by the present inventors that it would be advantageousto have a design that is compact in having both a low TTL/EFL ratio anda low ratio of front element diameter to image diagonal and thatachieves stable wide field of view image capture capability withtolerable, minimal, insubstantial, insignificant or drastically reduceddistortion and astigmatism characteristics. Wang et al. have proposed atU.S. Pat. No. 9,019,629 an optical assembly for a mobile phone camerathat exhibits a ratio of the sensor diagonal to the focal length between1.27 and 1.55. The optical assembly of Wang et al. is not howeverconfigured for capturing images at a wide field of view.

It is also recognized by the present inventors that it would beadvantageous to have a compact camera design that is carefullyconfigured to suppress negative effects from stray light and achievehigh dynamic range (HDR) imaging. It is therefore desired to have anoptical design wherein near normal incidence surfaces are significantlyavoided and at least 90% of return ghost foci are displaced at least 2mm from the image sensor plane. In addition, it is desired to achieve astray light irradiance ratio that is significantly below 1/1000, andeven significantly below 1/10,000 in certain embodiments, andapproximately at, or not greater than, or below 1/100,000 in certainembodiments, and a stray light power ratio that is significantly below1/100 and approximately at, or not greater than, or below 1/1000 incertain embodiments.

As image sensor technology continues to improve, ever higher pixeldensities are being achieved so that camera miniaturization need notimply low image quality in terms of resolution and contrast. It istherefore desired to have an optical assembly that has a high modulationtransfer function or MTF at the Nyquist and half Nyquist frequencies. Inthis same context, it is desired to have an optical assembly capable ofproducing images without lateral chromatic aberrations larger than 2-3pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically illustrates an optical assembly for a point actioncamera in accordance with certain embodiments.

FIG. 1B is a ray trace diagram for the optical assembly illustratedschematically in FIG. 1A.

FIG. 2 is a plot of aspheric sag versus radial distance from the centerof the asphere for the fifteenth surface from the object, or the objectside surface of the seventh lens element E8(A), in the example opticalassembly illustrated schematically in FIG. 1A.

FIG. 3 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the fifteenth surface from the object, orthe object side surface of the seventh lens element E8(A), in theexample optical assembly illustrated schematically in FIG. 1A.

FIGS. 4A-4E and 5A-5E respectively show plots of tangential and sagittalray aberrations for the wide field of view objective assemblyillustrated in FIG. 1A.

FIG. 6 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 1A normal to the opticalaxis (F1), 15 degrees from normal to the optical axis (F2), 35 degreesfrom normal to the optical axis (F3), 55 degrees from normal to theoptical axis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 7 illustrates diffraction modulation transfer function (MTF) plotsof modulation vs. defocussing position for tangential and sagittal raysimpinging upon the optical assembly of FIG. 1A normal to the opticalaxis (F1), 14 degrees from normal to the optical axis (F2), 28 degreesfrom normal to the optical axis (F3), 39.2 degrees from normal to theoptical axis (F4), and 56 degrees from normal to the optical axis (F5).

FIG. 8 shows astigmatic field curves for tangential fan (T) and sagittalfan (S) for the optical assembly illustrated schematically at FIG. 1A.

FIG. 9A schematically illustrates another optical assembly for a pointaction camera in accordance with certain embodiments.

FIG. 9B is a ray trace diagram for the optical assembly illustratedschematically in FIG. 9A.

FIG. 10 is a plot of aspheric sag versus radial distance from the centerof the asphere for the fifteenth surface from the object, or the objectside surface of the seventh lens element E7(A), in the example opticalassembly illustrated schematically in FIG. 9A.

FIG. 11 is a plot of slope of aspheric sag versus radial distance fromthe center of the asphere for the fifteenth surface from the object, orthe object side surface of the seventh lens element E7(A), in theexample optical assembly illustrated schematically in FIG. 9A.

FIGS. 12A-12D and 13A-13D respectively show plots of tangential andsagittal ray aberrations for the wide field of view objective assemblyillustrated in FIG. 9A.

FIG. 14 illustrates diffraction modulation transfer function (MTF) plotsof contrast vs. spatial frequency for tangential and sagittal raysimpinging upon the optical assembly of FIG. 9A normal to the opticalaxis (F1), 15 degrees from normal to the optical axis (F2), 35 degreesfrom normal to the optical axis (F3), 55 degrees from normal to theoptical axis (F4), and 75 degrees from normal to the optical axis (F5).

FIG. 15 illustrates diffraction modulation transfer function (MTF) plotsof modulation vs. defocussing position for tangential and sagittal raysimpinging upon the optical assembly of FIG. 9A normal to the opticalaxis (F1), 14 degrees from normal to the optical axis (F2), 28 degreesfrom normal to the optical axis (F3), 39.2 degrees from normal to theoptical axis (F4), and 56 degrees from normal to the optical axis (F5).

FIG. 16 shows astigmatic field curves for tangential fan (T) andsagittal fan (S) for the optical assembly illustrated schematically atFIG. 9A including the aspheric lens element E7(A). Also shown are thefield curves for a similar optical assembly except without an asphericlens element.

FIG. 17 shows a plot of Irradiance Ratio vs. Source Angle for an opticalassembly in accordance with the example embodiment illustrated at FIG.9A.

FIG. 18 shows a plot of Power Ratio vs. Source Angle for an opticalassembly in accordance with the example embodiment illustrated at FIG.9A.

BRIEF DESCRIPTION OF THE TABLES

Table 1 includes an Optical Design Prescription in accordance with afirst example embodiment. It is here noted that the Glasscode=xxxxxx.yyyyyy describes the refractive index (xxxxxx) anddispersion (yyyyyy) For example: 516800.641672 means that the refractiveindex n_(d)=1.5168 and the dispersion v_(d)=64.1672, each for the“d-line”, where the “d-line”=587.5618 nm (yellow helium line).

Table 2 includes Aspheric Sag Data Relative to Best Fit Sphere (SAG <10um) in accordance with the first example embodiment.

Table 3 includes quantitative data for a design of an aspheric elementE8(A) that enables multiple order astigmatism correction in accordancewith the first example embodiment.

Table 4 includes an Optical Design Prescription in accordance with asecond example embodiment. It is here noted that the Glasscode=xxxxxx.yyyyyy describes the refractive index (xxxxxx) anddispersion (yyyyyy) For example: 516800.641672 means that the refractiveindex n_(d)=1.5168 and the dispersion v_(d)=64.1672, each for the“d-line”, where the “d-line”=587.5618 nm (yellow helium line).

Table 5 includes Aspheric Sag Data Relative to Best Fit Sphere (SAG <12um) in accordance with the second example embodiment.

Table 6 includes quantitative data for a design of an aspheric elementE7(A) that enables multiple order astigmatism correction in accordancewith the second example embodiment.

TABLE 1 RDY THI RMD GLA >OBJ: INFINITY 5000.000000 1: 32.32500 1.800000882997.407651 2: 13.40000 8.175409 3: −51.80000 1.800000 496999.8154594: 16.95000 27.500000 5: 53.50000 4.000000 496999.815459 6: −18.600000.535248 7: −17.80000 1.800000 846660.237779 8: −24.86000 0.250000 9:20.40000 2.925000 882997.407651 10: 119.00000 4.929804 STO: INFINITY7.196775 12: −20.00000 1.800000 755199.275121 13: 9.12500 3.400000496999.815459 14: −112.50000 0.250000 15: 31.93637 3.160000496999.815459 ASP: A: −.154815E−04 B: 0.319205E−06 C: 0.110561E−07 D:−.243906E−09 E: 0.289139E−11 16: −30.98000 2.159011 17: 15.350005.000000 618000.633335 18: −31.72500 1.800000 523459.515405 19: 55.000001.018753 20: INFINITY 0.800000 516330.641420 21: INFINITY 3.000000 22:INFINITY 0.540000 516330.641420 23: INFINITY 1.160000 24: INFINITY0.000000 IMG: INFINITY 0.000000 SPECIFICATION DATA FNO 2.40000 DIM MM WL650.00 610.00 555.00 510.00 465.00 REF 3 WTW 1 2 4 2 1 YAN 0.0000018.00000 30.00000 42.00000 60.00000

TABLE 2 ASPHERIC EQUATION$Z = {\frac{({CURV})Y^{2}}{1 + \left( {1 - {\left( {1 + K} \right)({CURV})^{2}Y^{2}}} \right)^{1/2}} + {(A)Y^{4}} + {(B)Y^{6}} + {(C)Y^{8}} + {(D)Y^{10}}}$WHERE THE ASPHERIC COEFFICIENTS ARE AS FOLLOWS: A: −1.548150E−05 B:3.192050E−07 C: 1.105610E−08 D: −2.439060E−10 E: 2.891390E−12 ASPH SAGSAG Y (Z) SPHERE SAG DIFFERENCE 0.000000 0.000000 0.000000 −0.0078920.250000 0.000978 0.000993 −0.007878 0.500000 0.003913 0.003972−0.007834 0.750000 0.008803 0.008937 −0.007758 1.000000 0.0156450.015890 −0.007647 1.250000 0.024436 0.024831 −0.007497 1.5000000.035171 0.035763 −0.007300 1.750000 0.047848 0.048687 −0.0070522.000000 0.062461 0.063607 −0.006747 2.250000 0.079009 0.080524−0.006377 2.500000 0.097489 0.099442 −0.005939 2.750000 0.1179030.120365 −0.005430 3.000000 0.140256 0.143297 −0.004851 3.2500000.164557 0.168241 −0.004207 3.500000 0.190822 0.195204 −0.0035103.750000 0.219075 0.224190 −0.002777 4.000000 0.249350 0.255205−0.002037 4.250000 0.281691 0.288254 −0.001329 4.500000 0.3161560.323345 −0.000704 4.750000 0.352823 0.360484 −0.000231 5.0000000.391786 0.399678 0.000000 5.250000 0.433169 0.440936 −0.000125 5.5000000.477127 0.484265 −0.000754 5.750000 0.523860 0.529675 −0.0020776.000000 0.573629 0.577174 −0.004346 6.250000 0.626773 0.626773−0.007892

TABLE 3 Height (Y) Aspheric Sag (um) Height (Y) Aspheric Slope (um/mm)0.000 −7.892 0.000 0.000 0.250 −7.878 0.250 0.056 0.500 −7.834 0.5000.176 0.750 −7.758 0.750 0.304 1.000 −7.647 1.000 0.444 1.250 −7.4971.250 0.600 1.500 −7.300 1.500 0.788 1.750 −7.052 1.750 0.992 2.000−6.747 2.000 1.220 2.250 −6.377 2.250 1.480 2.500 −5.939 2.500 1.7522.750 −5.430 2.750 2.036 3.000 −4.851 3.000 2.316 3.250 −4.207 3.2502.576 3.500 −3.510 3.500 2.788 3.750 −2.777 3.750 2.932 4.000 −2.0374.000 2.960 4.250 −1.329 4.250 2.832 4.500 −0.704 4.500 2.500 4.750−0.231 4.750 1.892 5.000 0.000 5.000 0.924 5.250 −0.125 5.250 −0.5005.500 −0.754 5.500 −2.516 5.750 −2.077 5.750 −5.292 6.000 −4.346 6.000−9.076 6.250 −7.892 6.250 −14.184

TABLE 4 RDY THI RMD GLA > OBJ: INFINITY 5000.000000 1: 21.17500 2.750000882997.407651 2: 7.60000 5.105000 3: −37.00000 1.400000 496999.815459 4:11.50000 2.413000 5: −54.60000 1.400000 496999.815459 6: 14.850003.400000 737999.322613 7: −37.42500 2.920000 8: 12.70000 1.400000808095.227608 9: 9.00000 3.175000 618000.633335 10: −24.70000 2.017500STO: INFINITY 3.067000 12: −21.93390 2.000000 496999.815459 ASP:A:−.242148E−03 B: −.719194E−06 C:−.953571E−07 D:0.000000E+00 13:−24.75000 0.720000 14: −16.72500 1.400000 761821.265179 15: 17.500003.925000 618000.633335 16: −14.62500 1.095000 17: 22.70000 2.815000618000.633335 18: 113.27500 0.700000 19: 15.81000 3.480000 618000.63333520: 56.70000 2.560134 21: INFINITY 0.840000 516330.641420 22: INFINITY4.721276 23: INFINITY 0.540000 516330.641420 24: INFINITY 1.160000 25:INFINITY 0.000000 IMG: INFINITY 0.000000 SPECIFICATION DATA FNO 2.40000DIM MM WL 650.00 610.00 555.00 510.00 465.00 REF 3 WTW 1 2 4 2 1 YAN0.00000 30.00000 42.00000 60.00000

TABLE 5 ASPHERIC EQUATION$Z = {\frac{({CURV})Y^{2}}{1 + \left( {1 - {\left( {1 + K} \right)({CURV})^{2}Y^{2}}} \right)^{1/2}} + {(A)Y^{4}} + {(B)Y^{6}} + {(C)Y^{8}} + {(D)Y^{10}}}$WHERE THE ASPHERIC COEFFICIENTS ARE AS FOLLOWS: A: −0.242148E−03 B:−0.719194E−06 C: −0.953571E−07 CURVATURE OF BEST SPHERE = −0.051948RADIUS OF BEST SPHERE = −19.250 ASPH SAG SPHERE SAG Y (Z) SAG DIFFERENCE0.000000 0.000000 0.000000 0.000000 0.140000 −0.000447 −0.000509−0.000062 0.280000 −0.001789 −0.002036 −0.000248 0.420000 −0.004029−0.004582 −0.000553 0.560000 −0.007174 −0.008147 −0.000973 0.700000−0.011231 −0.012731 −0.001500 0.840000 −0.016211 −0.018336 −0.0021250.980000 −0.022128 −0.024962 −0.002834 1.120000 −0.028996 −0.032609−0.003613 1.260000 −0.036834 −0.041281 −0.004446 1.400000 −0.045662−0.050977 −0.005314 1.540000 −0.055504 −0.061699 −0.006195 1.680000−0.066385 −0.073449 −0.007065 1.820000 −0.078334 −0.086229 −0.0078961.960000 −0.091383 −0.100042 −0.008659 2.100000 −0.105568 −0.114888−0.009320 2.240000 −0.120927 −0.130771 −0.009844 2.380000 −0.137505−0.147694 −0.010189 2.520000 −0.155348 −0.165658 −0.010310 2.660000−0.174508 −0.184667 −0.010160 2.800000 −0.195043 −0.204725 −0.0096812.940000 −0.217019 −0.225833 −0.008815 3.080000 −0.240504 −0.247997−0.007493 3.220000 −0.265578 −0.271219 −0.005641 3.360000 −0.292330−0.295504 −0.003174 3.500000 −0.320855 −0.320855 0.000000

TABLE 6 Height (Y) Aspheric Sag (um) Height (Y) Aspheric Slope (um/mm)0.000 0.000 0.000 0.000 0.140 −0.062 0.140 −0.443 0.280 −0.248 0.280−1.329 0.420 −0.553 0.420 −2.179 0.560 −0.973 0.560 −3.000 0.700 −1.5000.700 −3.764 0.840 −2.125 0.840 −4.464 0.980 −2.834 0.980 −5.064 1.120−3.613 1.120 −5.564 1.260 −4.446 1.260 −5.950 1.400 −5.314 1.400 −6.2001.540 −6.195 1.540 −6.293 1.680 −7.065 1.680 −6.214 1.820 −7.896 1.820−5.936 1.960 −8.659 1.960 −5.450 2.100 −9.320 2.100 −4.721 2.240 −9.8442.240 −3.743 2.380 −10.189 2.380 −2.464 2.520 −10.310 2.520 −0.864 2.660−10.160 2.660 1.071 2.800 −9.681 2.800 3.421 2.940 −8.815 2.940 6.1863.080 −7.493 3.080 9.443 3.220 −5.641 3.220 13.229 3.360 −3.174 3.36017.621 3.500 0.000 3.500 22.671

DETAILED DESCRIPTIONS OF THE EMBODIMENTS

A compact wide field of view digital camera and an optical assembly fora compact wide field of view digital camera are provided herein. Theoptical assembly includes at least two optical groups that are separatedby an aperture stop. The first optical group is configured to collectivelight at a wide field of view. The optical layout is designed to providelow distortion and low aberrational error. An aspheric lens element isprovided to reduce astigmatism.

The embodiments described in detail herein provide several advantageousfeatures. In certain embodiments, the optical assembly is designed toprovide a high dynamic range (HDR) & high resolution (HR) imagery. Fourthousand (4K) pixels or more are resolvable across the horizontal fieldof view of the optical assembly in accordance with certain embodiments.An optical assembly in accordance with certain embodiments exhibits ahigh MTF at the Nyquist frequency (˜200 lp/mm) and/or a high MTF thrufocus at ½ Nyquist (˜100 lp/mm). The optical assembly covers a widerfield of view than contemporary objectives, e.g., 120 degrees or more.In certain embodiments, a number of resolvable spots within a sensoractive area is enhanced in accordance with a larger space bandwidthproject, and lateral chromatic aberration (LCA) is less than two pixelsor less than 5 microns and color fringing is avoided.

An optical assembly in accordance with certain embodiments exhibits lowfield curvature and suppresses the impact of stray light. An opticalassembly in accordance with certain embodiments exhibits a low ratio offront element diameter relative to image diagonal even though images arecaptured at a wide field of view with low distortion and low astigmatismcharacteristics. In certain embodiments, an IR cut filter is integratedinto a housing for the optical assembly. In certain embodiments, theoptical assembly includes three or four optical groups, and atelecentric cone is delivered to an image sensor plane.

An optical assembly in accordance with certain embodiments is designedto avoid causing stray light to impact image quality. As such, twosurface ghosts or double bounce ghosts from lens surfaces, ghostingoriginating from sensor and subsequent reflections from lens surfacesback to the image sensor, and scattered light from mechanical structuresand edges of lens elements are suppressed in the design of the opticalassembly. Stray light contributions are avoided in the optical designprocess by reducing the number and location of near normal incidencesurface for both marginal and chief rays, wherein the angle of incidenceor refraction of these rays is ˜0 degrees. Since any pair of surfacescan generate a ghost image in a design with n surfaces, there aren(n−1)/2 potential ghost images that are formed. The key to developing adesign with exceptional stray light rejection properties is themanagement of where these secondary ghost images come to focus. Toaccomplish this, a “keep out” zone is defined wherein ghost images mustform more than +/−2 mm from the sensor plane. In certain embodiments,more than 90% of return ghost foci are disposed outside of this +/−2 mmkeep out zone. In certain embodiments, more than 90% of return ghostsfoci are disposed more than +/−2 mm from sensor.

An optical assembly is provided for a point action camera having a widefield of view in excess of 120 degrees. The optical assembly hasmultiple lens elements including at least one lens element that has anaspheric lens surface. The optical assembly exhibits a modulationtransfer function (hereinafter “MTF”) at Nyquist frequency that is above0.3 and a MTF at half Nyquist frequency that is above 0.5 across thewide field of view. In certain embodiments, the MTF at Nyquist frequencyis above 0.35 and the MTF at half Nyquist frequency is above 0.55.

Another optical assembly is provided for a point action camera having awide field of view in excess of 120 degrees. The optical assembly hasmultiple lens elements including one or more aspheric lens surfaces. Theoptical assembly exhibits less than five microns of lateral chromaticaberration. In certain embodiments or in combination with certain imagessensors, the optical assembly has less than two pixels of lateralchromatic aberration.

Another optical assembly is provided for a point action camera having awide field of view in excess of 120 degrees. The optical assembly hasmultiple lens elements including one or more aspheric lens surfaces. Aratio of a diameter of a first lens element at the object end of theoptical assembly to an image diagonal is less than approximately 3. Incertain embodiments, the first lens element has a convexo-concave ormeniscus shape and a diameter less than 30 mm, and in some embodimentsless than 25 mm, and in some embodiments is not more than 23 mm.

Another optical assembly is provided for a point action camera having awide field of view in excess of 120 degrees. The optical assembly hasmultiple lens elements including one or more aspheric lens surfaces. Theoptical assembly is configured such that 90% or more of return ghostfoci are displaced from the image sensor plane by at least +/−2 mm. Incertain embodiments, an irradiance ratio is less than 1/10,000 and astray light power ratio is less than 1/100. In addition, in certainembodiments, an advantageously low stray light irradiance ratio isachieved that is significantly below 1/1000, and even significantlybelow 1/10,000 in certain embodiments, and approximately at, or notgreater than, or below 1/100,000 in certain embodiments. Also, anadvantageously low stray light power ratio is achieved in certainembodiments that is significantly below 1/100 and approximately at, ornot greater than, or below 1/1000 in certain embodiments.

In certain embodiments, a ratio of total track length to effective focallength, or TTL/EFL, is less than 12, and in some embodiments, TTL/EFL isless than 8. The total track length is less than 10 cm in someembodiments.

From object end to image end, an optical assembly in accordance withcertain example embodiments includes first, second and third opticalgroups. The first optical group may include two or more lens elementsconfigured to collect and reduce a field angle of light incident at awide field of view in excess of 120 degrees. The second optical groupmay include one or two or more lens elements. The third optical groupmay include two or more lens elements, wherein at least one lens elementof the third optical group may include an aspheric surface that isconfigured to correct higher order astigmatism. An aperture stop may bedisposed between the second and third optical groups. In certainembodiments, the third optical group includes an IR cut filter. Incertain embodiments, the second and/or third optical groups may havethree lens elements or more.

In certain embodiments, the third optical group may include one or moredoublets. The third optical group may include a first doublet and asecond doublet. An aspheric lens element may be disposed between thefirst and second doublets.

The first optical group may include a convexo-concave or meniscus lens.A diameter of the convexo-concave or meniscus lens of the first opticalgroup may be less than 30 mm, and in certain embodiments less than 25mm. A ratio of the diameter of the convexo-concave or meniscus lens ofthe first optical group to an image size may be less than 3 in certainembodiments. The first optical group may also include a biconcave lens.

The second optical group may include, from object end to image end, abiconvex or quasi-planar-convex or planar-convex lens, a concavo-convexor meniscus lens, and a convexo-planar or convexo-quasi-planar orbiconvex lens.

The third optical group may include, from object end to image end, afirst doublet, an aspheric lens element and a second doublet. The firstdoublet may include a biconcave or quasi-planar-concave lens having animage facing surface attached to an object facing surface of aconvexo-planar or convexo-quasi-planar lens. The second doublet mayinclude a biconvex lens having an image facing side attached to anobject facing side of a biconcave lens or concavo-quasi-planar lens. AnIR cut filter may be included within the third optical group after thesecond doublet.

The optical assembly may include a fourth optical group that isconfigured to deliver a telecentric cone to the image sensor. The fourthoptical group may include a convexo-planar, convexo-quasi-planar orconvexo-concave lens element. The fourth optical group may furtherinclude a second convexo-planar, convexo-quasi planar or convexo-concavelens element.

The aspheric surface may have an aspheric sag that is less thanapproximately 10 microns in certain embodiments. The aspheric sag slopeof the aspheric surface may be less than approximately 15 microns permillimeter in certain embodiments.

An optical assembly in accordance with certain embodiments includes asingle aspheric lens element. That is, the single aspheric lens elementmay be the only aspheric lens element within the optical assembly. Inaccordance with these embodiments, lens elements other than the singleaspheric lens element may have spherical or planar lens surfaces, orboth, each without significant aspheric departure.

An optical assembly in accordance with certain embodiments may include asingle aspheric lens surface. That is, only one surface of a singleaspheric lens element in an optical assembly in accordance with theseembodiments has an aspheric departure. In accordance with theseembodiments, lens element surfaces other than the single aspheric lenssurface may have spherical or planar shapes, or both, withoutsignificant aspheric departure.

In certain embodiments, the optical assembly includes only one asphericlens element.

In certain embodiments, the optical assembly includes only one asphericlens surface.

A digital point action camera or other compact wide field of viewdigital camera is also provided that includes an optical assembly inaccordance with any of the embodiments described herein, as well as animage sensor disposed approximately at a focal plane of the opticalassembly. A digital camera housing may include electronics and a userinterface, and may be configured to contain the optical assembly and theimage sensor in optically effective relative disposition.

Another optical assembly is provided for a point action camera or otherwide field of view digital camera having a wide field of view includingmultiple lens elements and having at least one aspheric surface. Theoptical assembly is configured to provide a wide field of view, which isin certain embodiments in excess of 120 degrees. The optical assemblyincludes an inward field curvature of less than approximately 75microns. In certain embodiments, the inward field curvature is less thanapproximately 60 microns. In other embodiments, the inward fieldcurvature is less than approximately 50 microns.

Another optical assembly is provided for a point action camera having awide field of view, including multiple lens elements, and having atleast one aspheric surface. This optical assembly is configured toprovide a field of view in excess of 120 degrees and exhibits no morethan 0.7 mm of longitudinal astigmatism.

Another optical assembly is provided for a point action camera having awide field of view, including multiple lens elements, and having atleast one aspheric surface. This optical assembly is configured toprovide a field of view in excess of 120 degrees and exhibits a ratio oftotal track length to effective focal length that is less than 8.

Another optical assembly is provided for a point action camera having awide field of view in excess of 150 degrees, including multiple lenselements, and having at least one aspheric surface with no more than 30microns of aspheric sag and no more than 25 microns/millimeter ofaspheric sag slope.

In certain embodiments, the longitudinal astigmatism comprisesapproximately 0.6 mm or less, or in other embodiments, approximately 0.5mm or less, or approximately 0.3 mm or less, or approximately 0.2 mm orless, or approximately 0.1 mm or less in certain embodiments.

From object end to image end, an optical assembly in accordance withcertain embodiments includes a first optical group and a second opticalgroup, wherein the first optical group is configured to collect light ata wide field of view and a second optical group is configured to correctdistortion or astigmatism error or both. An aperture stop may bedisposed between said first and second optical groups. Alternatively,the optical assembly may include a third optical group and the aperturestop may be disposed between the second and third optical groups. Theoptical assembly may also include a fourth optical group.

The first optical group may include two or more convexo-concave ormeniscus lenses. The first optical group may include a biconvex lens.

The second and/or third optical group may be configured to correctastigmatism error. The second or third optical group may includemultiple lens elements including a lens element that is configured withan aspheric departure to correct astigmatism error. In certainembodiments, the ultimate or penultimate lens element of the opticallens assembly includes an aspheric departure, while an aspheric lenselement may be provided adjacent just after the aperture stop. Incertain embodiments, an object facing surface of this lens element hasan aspheric departure. The optical assembly may include seven or eightor more lens elements, including one or more doublets.

A second, third or fourth optical group (from object to image) mayinclude three or four lens elements. The second optical group mayinclude, from object side to image side, a first singlet, a doublet anda second singlet. The first singlet may include a biconvex orplano-convex or quasi-plano-convex lens. The second singlet may includea biconvex, or convexo-plano or convexo-quasi-plano lens. The doubletmay include in certain embodiments, from object side to image side, abiconcave lens and a biconvex lens.

A third optical group may be disposed after the second optical group orbetween the first and second optical groups. The third optical group mayinclude one or two doublets. The third optical group may include anaspheric lens element. The aspheric lens element may be disposed betweenthe aperture stop and a doublet, or between a pair of doublets.

The optical assembly may include a fourth optical group that is disposedafter the third optical group and configured to deliver a telecentriccone to the image sensor. The fourth optical group may include aconvexo-planar, convexo-quasi-planar or convexo-concave lens element.The fourth optical group may further include a second convexo-planar,convexo-quasi planar or convexo-concave lens element.

The lateral chromatic aberration (LCA) of an optical assembly inaccordance with certain embodiments may be less than approximately threepixels. The LCA in certain embodiments may be less than approximatelytwo pixels. The LCA in certain embodiments may be less thanapproximately five microns or less than approximately three microns.

An optical assembly in accordance with certain embodiments may include asingle aspheric lens element, which may be the only aspheric lenselement within the optical assembly. In these embodiments, lens elementsother than the single aspheric lens element have spherical or planarlens surfaces, or both, each without significant aspheric departures.

An optical assembly in accordance with certain embodiments may include asingle aspheric lens surface, which may be the only aspheric lenssurface within the optical assembly. In these embodiments, lens surfacesother than the single aspheric lens surface have spherical or planarlens surfaces, or both, each without significant aspheric departures.

Another optical assembly in accordance with certain embodiments includesonly one aspheric lens element. Subsets of these embodiments includelens elements that have two aspheric surfaces, i.e., both the objectfacing surface and the image facing surface of a same aspheric lenselement are configured with aspheric departure. Other subsets of theseembodiments include lens elements that have only a single aspheric lenssurface, i.e., either the object facing surface or the image facingsurface is aspheric, while the other surface does not have significantaspheric departure or to tolerance one of the lens surfaces isspherical.

Another optical assembly in accordance with certain embodiments includesonly one aspheric lens surface. This optical assembly includes a singleaspheric lens surface configured to correct astigmatism.

A digital point action camera is provided that includes any of theoptical assemblies described herein, along with an image sensor disposedapproximately at a focal plane of the optical assembly. A digital camerahousing includes electronics and a user interface, and contains anddurably affixes the optical assembly and the image sensor in opticallyeffective relative disposition. The housing may be waterproof and mayinclude shock absorbing material to withstand shocks such as may becaused by collisions or sudden acceleration or high speed or highfrequency jitter.

An aspheric lens element is provided for an optical assembly of a widefield of view point action camera in accordance with any of theembodiments of optical assemblies or point action cameras describedherein. In certain embodiments, one or both surfaces has anapproximately 30 microns or less sag and an approximately 25microns/millimeter or less aspheric sag slope. In a specific embodiment,only a single lens surface has aspheric departure. In anotherembodiment, both the image facing surface and the object facing surfaceof the same lens element include aspheric departures.

In addition, combinations of features described herein, above and/orbelow, with regard to different embodiments form additional embodimentsof optical assemblies, point action cameras and aspheric lens elements.Features of embodiments of optical assemblies that include two lensgroups may be combined with those that include three lens groups. Forexample, the first and second lens groups G1 and G2, of an opticalassembly that includes three lens groups, G1, G2 and G3, may be thoughtof as an optical assembly having a first lens group G1′=G1+G2 and asecond lens group G2′=G3, or alternatively G1′=G1 and G2′=G2+G3.

Several example embodiments are described below and are illustrated inthe accompanying drawings. In certain embodiments, a seventh lenselement, from object to image, is the only lens element of the opticalassembly that includes one or two aspheric surfaces. In the example ofFIG. 1A, the E6/E7 doublet may be considered to be a single lenselement, the sixth lens element of the optical assembly illustratedschematically in FIG. 1A, such that the singlet E8(A) can be consideredto be the seventh lens element in that optical assembly.

In certain embodiments, the object facing surface of the seventh lenselement, or the thirteenth or fifteenth surface of the optical assembly,has an aspheric departure. The image facing surface of the seventh lenselement, or the fourteenth or sixteenth lens surface of the opticalassembly, may have an aspheric surface also, or may alternatively have aspherical surface that may be slightly curved or quasi-planar, or mayhave a significant spherical curvature, or may be approximately planar.

Alternatively, the fourteenth and/or sixteenth lens surfaces may be theonly surface or surfaces of the optical assembly that has an asphericdeparture, while the thirteenth and/or fifteenth surfaces may have aplanar, quasi-planar or convex spherical curvature. The single lenselement of the optical assembly that has aspheric departure in certainembodiments may be the fifth or sixth or eighth lens element rather thanthe seventh, or may be instead the first or the second lens element. Inthese alternative embodiments, one or both surfaces of the singleaspheric lens element may have aspheric departure, and in thoseembodiments wherein only a single lens surface has aspheric departure,the other surface of the aspheric lens element may be planar, or may bequasi-planar or slightly spherically curved, or may be significantlyspherical.

Example Embodiments

Referring to the example illustrated schematically in FIGS. 1A-1B, andin the plots shown in FIGS. 2-8, and quantitatively at Tables 1-3, anoptical assembly in accordance with certain embodiments may include afirst lens group G1, a second lens group G2 and a third lens group G3.The first lens group G1 is disposed nearer to the object or scene thatis being imaged than the second lens group G2. The second lens group G2is disposed between the first lens group G1 and the third lens group G3.The image plane lies just beyond the third lens group G3. Together, thefirst, second and third optical groups G1, G2 and G3, respectively,cover a wide field of view, i.e., greater than 120 degrees, or incertain embodiment greater than 135 degrees and in others greater than150 degrees and even in certain embodiments significantly close to 180degrees. Alternatively, there may be two, or four or more, lens groupsinstead of three, or the entire optical assembly may form a single lensgroup.

Generally speaking, the lens group G1 is configured to collect widefield rays and reduce the field angle to groups G2 and G3. The group G2is configured to provide advantageously low axial chromatic aberrationand spherochromatism or variation of spherical with wavelength. Forexample, in certain embodiments the axial chromatic aberration, as maybe defined by the ray trace at the 0.7 zonal in the pupil, is less than0.025 microns across the spectral band, e.g., from 465 nm to 650 nm. Thearrangement of G2 and G3 about the aperture stop advantageously balancesfield aberrations of multiple orders. The placement and configuration ofthe asphere E8(A) advantageously corrects higher order astigmatism.

The lens groups G2 and G3 are configured such that the optical assemblyproduces advantageously low imaging errors from aberrations, andparticularly distortion and astigmatism. However, the configuration caninclude contributions within the second lens group G2 to the collectionand reduction of wide field rays and/or contributions within the firstlens group G1 to the correction of aberrations such as distortion andastigmatism. For example, one or more lens elements of the group G2 mayhave a material or shape characteristic tending to facilitate collectionof wide angle rays and/or a surface of a lens element of group G1 mayhave aspheric departure configured to assist in the correction ofaberrations.

In the embodiment illustrated schematically at FIGS. 1A-1B, the firstlens group G1 includes two lenses from furthest to closest to the imageplane, namely lens E1, and lens E2. Lens E1 comprises a convexo-concavelens, or meniscus, in the example embodiment of FIGS. 1A-1B. This meansthat the object facing surface of lens E1, which is the first surface ofthe optical assembly of the example embodiment of FIGS. 1A-1B, has aconvex shape tending to converge incident light, while the image facingsurface of lens E1, which is the second surface of the optical assemblyof FIGS. 1A-1B, has a concave shape tending to diverge incident light.The lens E1 has a nominal overall optical power. This lens E1 may havean extended radius outside of an active radius which assists andfacilitates a wide field of view feature of the optical assembly ofFIGS. 1A-1B. The physical dimensional characteristics of the lenses ofthe optical assemblies of the embodiments described herein generallypermit configuring the wide field of view optical assembly within a lensbarrel of a point action camera and/or within a compact or miniaturepoint action camera.

The lens E1 may be fixed, i.e., relative to the image plane and otherfixed elements of the system. Alternatively, the lens E1 may be movableto permit focusing by automatic or manual actuation using, e.g., a voicecoil motor, piezo, or MEMS coupled to the lens E1. In this alternativeembodiment, a feedback based on analysis of image data received at theimage sensor by a processor, an image processor or an image signalprocessor (ISP). Another optical group may include one or more movablelenses, mirrors or other optics. For example, in certain embodiments thelens E1 is fixed and one or more or all of the other lenses are movable,and in certain embodiments the entire optical assembly in movablerelative to the image sensor. In this context, a zoom feature may alsobe provided optically and/or electronically. Thus, embodiments of pointaction cameras described herein include fixed focus, autofocus andautofocus zoom point action cameras. In certain embodiments, the lens E1has an index of refraction at the sodium d line (i.e., 587.5618 nm) ataround 1.88, or n(λ_(d))≈1.9. The dispersion may be around 41. The lensE1 has little overall optical power, as mentioned, and serves primarilyas a collecting lens that facilitates the wide field of view of theoptical assembly.

Lens E1 has a larger diameter in order to collect rays at outer edges ofthe wide field of view and reduces the field angle for the subsequentlenses of the optical assembly. Lens group G1, and particularly lensesE1 and E2, generally serves to reduce the ray angle for the group G2 andG3 lens elements. Lens groups G2 and G3 generally serve to balance orcorrect field aberrations of multiple orders, including distortion andastigmatism errors. The overall optical design of the lens groups G2 andG3 generally serves to correct distortion, while the aspheric fifteenthsurface of the optical assembly of FIGS. 1A-1B generally serves tocorrect higher order astigmatism.

The lens element E2 of the lens group G1 has a biconcave orplano-concave or quasi-plano-concave structure in the example of FIGS.1A-1B. In other words the object facing surface of the lens E2, which isthe third surface of the optical assembly of FIGS. 1A-1B, has a slightlyor nominally concave or planar surface shape, while the image facingsurface of the lens E2, or the fourth surface of the optical assembly ofFIGS. 1A-1B, has a concave shape tending to diverge incident light rays.The lens E2 has a negative overall focal length and serves as adiverging optical element. In certain embodiments, the lens E2 has anindex of refraction at the sodium d line (i.e., 587.5618 nm) at around1.5, or n(λ_(d))≈1.5. The dispersion may be around 82.

The lens group G1 has an overall negative focal length, e.g., in oneembodiment EFL (G1)≈−11.3 mm, and serves to collect and convergeincoming light from an object, group of objects or a foreground,background or overall scene, including a wide field of view greater than90 degrees in the horizontal and/or vertical dimensions, and typically120, 135, or 150 degrees or more in the horizontal and/or 110-120degrees or more in the vertical. The rays received from the opticalgroup G1 are further optically reduced by optical group G2, which has apositive focal length, e.g., in one embodiment EFL (G2)≈17.2 mm. Opticalgroup G2 serves to correct aberrations such as distortion before imagesare captured by an image sensor of a point action camera for viewing ona display, and/or for recording or storage or for data analysis,monitoring, security or surveillance and/or for transmission and/orimage processing.

The optical group G2 in the example of FIGS. 1A-1B includes three lenselements E3, E4 and E5, while the lens group G3 in the example of FIGS.1A-1B includes the rest of the lenses of the optical assembly E6-E10.

The lens element E3 comprises a functionally converging optical elementand has a biconvex structure in the illustrative example of FIGS. 1A-1B.Both the object facing and image facing surfaces of the lens element E3,which are the fifth and sixth surfaces of the optical assembly that isillustrated schematically in the example embodiment of FIGS. 1A-1B, areconvex and tend to converge incident light. In certain embodiments, thelens element E3 has a strongest positive optical power among theelements of group G2. In certain embodiments, the lens E3 has an indexof refraction at the sodium d line (i.e., 587.5618 nm) at around 1.5, orn(λd)≈1.5. The dispersion may be around 82. In certain embodiments, thelens elements E2 and E3 are formed from a same or similar material.

Lens E4 may have a concavo-convex or meniscus shape. That is, the objectfacing surface of lens E4, which is the seventh surface of the opticalassembly of FIG. 1A, has a concave shape tending to diverge incidentlight, while the image facing surface of the lens E4, which is theeighth surface of the optical assembly of FIG. 1A, has a convex shapetending to converge incident light. The lens E4 is disposed in theexample of FIGS. 1A-1B just after lens E3. The shapes of the sixth andseventh surfaces may be similar in certain embodiments such that only asmall gap exists between the lenses E3 and E4 substantially along theirradii from center to edge. The lens E4 has nominal overall opticalpower. In certain embodiments, the lens E4 has an index of refraction atthe sodium d line (i.e., 587.5618 nm) at around 1.85, or n(λ_(d))≈1.85.The dispersion may be around 24.

The lens E5 has a convexo-planar or convexo-quasi-planar shape. Theninth and tenth surfaces of the optical assembly of FIG. 1A respectivelyexhibit convex and planar or quasi-planar shapes. Thus, the lens E5tends to converge incident light rays before the aperture stop.

The lens group G2 may include one or two lenses, or four or more lenses,instead of the three lenses E3-E5 shown in the example of FIG. 1A.

An aperture stop is disposed between the lens element E5 and the lenselement E6 in the example of FIG. 1A. Alternatively, an aperture stop isdisposed between the lens groups G1 and G2, whatever number of opticalelements each may comprise. An aperture stop may be located differentlyand there may be one or more additional apertures within the opticalassembly.

The lenses E6 and E7 of the lens group G3 are coupled together to form adoublet. In certain embodiments, the image facing surface of lens E6 andthe object facing surface of the lens E7 are in direct contact. Anadhesive or other standard process of coupling constituent lenses of adoublet may be used, which process may depend upon the materials of theconstituent lenses E6 and E7. In certain embodiments, the lens E6 has anindex of refraction at the sodium d line (i.e., 587.5618 nm) at around1.75, or n(λ_(d))≈1.75. The dispersion of lens E6 may be around 28. Incertain embodiments, the lens E7 has n(λ_(d))≈1.5. In certainembodiments, the lens E7 has a dispersion around 82. In certainembodiments, the lens E7 may be formed from a same or similar materialas lenses E2 and E3. The doublet overall serves to configure the lightrays before becoming incident upon the lens element E8(A).

Referring to FIGS. 1A-1B, there a significant advantage to having anoptical assembly in accordance with certain embodiments, wherein theE6/E7 doublet, which is shown disposed between the fifth singlet E5 andthe asphere E8(A) in FIGS. 1A-1B, is configured to correct obliqueaberrations.

The lens element E8(A) has a biconvex shape. The object facing surfaceof the lens E8(A), which is the fifteenth surface of the opticalassembly of FIGS. 1A-1B, has a convex shape which relatively stronglyconverges incident light. The fifteenth surface of the optical assemblyof FIGS. 1A-1B also has a significant aspheric departure in this exampleembodiment. The image facing surface of the lens E8(A), which is thesixteenth surface of the optical assembly of FIGS. 1A-1B, also has aconvex shape. In certain embodiments, the lens E8(A) has an index ofrefraction at the sodium d line (i.e., 587.5618 nm) at around 1.5, orn(λ_(d))≈1.5. The dispersion of the lens E8(A) may be around 82. Thelens E8(A) may be formed from same or similar material as lenses E2, E3and E7.

A second doublet E9/E10 is disposed after the E8(A) singlet. In certainembodiments, the image facing surface of lens E9 and the object facingsurface of the lens E10 are in direct contact. An adhesive or otherstandard process of coupling constituent lenses of a doublet may beused, which process may depend upon the materials of the constituentlenses E9 and E10. In certain embodiments, the lens E9 has an index ofrefraction at the sodium d line (i.e., 587.5618 nm) at around 1.62, orn(λd)≈1.62. The dispersion of lens E9 may be around 63. In certainembodiments, the lens E10 has n(λd)≈1.5. In certain embodiments, thelens E10 has a dispersion around 52. The second doublet in the exampleof FIGS. 1A-1B overall serves to configure the light rays beforebecoming incident upon the image sensor.

Between the twentieth surface of the optical assembly of FIGS. 1A-1B andthe image plane are an IR filter and a cover plate. The IR filter servesto cut out infrared light that can otherwise interfere with the functionof a silicon-based image sensor to collect visible image data. Incertain embodiments, the IR filter is disposed within a same housing asthe optical assembly or the groups G2 and G3 if the group G1 isseparately packaged or the group G3 if groups G1 and G2 are separatelypackaged. The cover plate serves to protect the image sensor fromincident dust, water, oxygen or other corrosive or artifact producingelements that may be present in the ambient space surrounding the pointaction camera. A separate baffle may be included to reduce the amount ofstray light that may become otherwise incident upon the image sensor.Each of the IR filter and the cover glass may have a refractive indexaround 1.5 and a dispersion around 64. For example, NBK7 Schott glassmay be used.

The aspheric departure of the fifteenth optical surface of the opticalassembly in the example embodiment of FIGS. 1A-1B serves toadvantageously significantly reduce higher order astigmatism errors thatwould be otherwise inherent in a wide field of view system without anaspheric surface in accordance with embodiments described herein.Moreover, the advantageous design of the optical assembly of FIGS.1A-1B, and specifically of the second and third optical groups G2 andG3, and more specifically of the aspheric lens element E8(A), and stillmore specifically of the aspheric object facing surface of the lenselement E8(A) permits the optical assembly in this embodiment to have amore efficient manufacturability than conventional designs that containmultiple aspheric surfaces and/or multiple aspheric lenses or otheroptical elements.

The example embodiment of FIGS. 1A-1B has H(θ)/f*θ=1.078. In anothersimilar embodiment H(θ)/f*θ=1.174. In other embodiments, H(θ)/f*θ isgreater than 1.2, 1.3, 1.4 and even 1.5, and in other embodimentsH(θ)/f*θ is approximately 1.

Table 1 generally discloses certain specifications of the exampleoptical assembly that is represented schematically in side view in FIG.1A. Table 1 lists RDY, which is the radius of curvature of the opticalsurface. Table 1 lists THI which are the thicknesses of the lensesE1-E10 and the spaces between the lenses E1-E10 in sequential order. Therow 1 thickness describes the thickness of the first lens E1 in thisembodiment. The row 2 thickness describes the thickness of the spacingbetween the first lens E1 and second lens E2. The spacing may includeair, or for example dry air or nitrogen gas or vacuum or a noble gas, ora liquid such as water. The row 3 describes the thickness of the secondlens E2. The row 4 describes the air spacing between the second lens E2and the third lens E3 in this example. The row 5 describes the thicknessof the third lens E3. The row 6 describes the thickness of the spacingbetween the third lens E3 and the fourth lens E4. The row 7 describesthe thickness of the fourth lens E4 in this example. The row 8 describesthe thickness of the spacing between the fourth lens E4 and the fifthlens E5. The row 9 describes the thickness of the fifth lens E5. The row10 describes the thickness of the spacing between the fifth lens E5 andthe aperture stop. The row STO describes the thickness of the airspacing between the aperture stop and the sixth lens E6. The row 12describes the thickness of the sixth lens E6. The row 13 describes thethickness of the seventh lens E7. There is no spacing between the lensesE6 and E7 in this example wherein the lens element E6/E7 is a doublet.The row 14 describes the spacing between the E6/E7 doublet and theeighth lens E8(A). The row 15 describes the thickness of the eighth lensE8(A). The aspheric coefficients A-E for the eighth lens E8(A) areprovided just below the row 15. The aspheric equation is provided at thetop of Table 2. The row 16 describes the thickness of the spacingbetween lens E8(A) and lens E9. The row 17 describes the thickness ofthe lens E10. There is no spacing between the lens E9 and the lens E10in this example wherein the lens element E9/E10 is a doublet. The row 19describes the thickness between the E9/E10 doublet and the IR cutfilter. The row 20 describes the thickness of the IR cut filter. The row21 describes the spacing between the IR cut filter and the sensor coverglass. The row 22 describes the thickness of the sensor cover glass. Therow 23 describes the thickness of the spacing between the sensor coverglass and the image plane.

Eight lens elements including six singlets and two doublets, or tenlenses E1-E10 make up the example optical assembly that is illustratedschematically at FIG. 1A, while a point action camera includes the IRcut filter, cover glass and an image sensor packaged within a housingalong with the optical assembly. The first two lens elements E1-E2 forma first optical group G1, the next three lens elements E3-E5 form thesecond optical group G2, and the final three lens elements includingfive lenses E6-E10 form the third optical group G3.

The radii of curvature are, in the single aspheric surface example,approximately, i.e., within manufacturing tolerances, the sameeverywhere along the optical surface for each of the first throughfourteenth and sixteenth through twentieth surfaces of the opticalassembly of FIG. 1A. In Table 1, the row 12 describes the curvature ofboth the twelfth and thirteenth surfaces, which are the image facingsurface of the lens E6 and the object facing surface of the lens E7,which have the same curvature. Likewise, the row 17 in Table 1 describesthe curvature of both the eighteenth and nineteenth surfaces, which arethe image facing surface of the lens E9 and the object facing surface ofthe lens E10, which have the same curvature. That is, the coefficients Athru E are each approximately zero for 19 out of 20 surfaces of theembodiment of FIG. 1A in the single aspheric surface example of a widefield of view optical assembly for a point action camera or compactcamera, or miniature camera module or other camera or camera moduleincluding a single aspheric lens element, or only one aspheric lenselement, and exhibiting advantageously low distortion and lowastigmatism, as well as high MTF at Nyquist and half Nyquistfrequencies, and low lateral chromatic aberration, and compactness inthree spatial dimensions. The departures from spherical of the fifteenthsurface are represented in Table 1 as nonzero coefficients A-E, whichcorrespond mathematically to the coefficients indicated in the formulathat is provided above the Table 2 in the illustration.

This formula with the non-zero coefficients A-E as indicated in Table 1represent the aspheric curvature of the surface 15 or object facingsurface of the lens E8(A) of the example optical assembly that isillustrated schematically in FIG. 1A.

The specification data of Table 1 represent the first order softwareinputs to complete the optical model. FNO is F number and isapproximately 2.4 in this example. DIM is the dimension which is mm. WLare the wavelengths which are in nanometers, and are 650 nm (red), 610nm (orange), 555 nm (yellow), 510 nm (green) and 465 nm (blue) in thisexample.

Table 2 shows aspherical and spherical SAG data for the fifteenthsurface of the optical assembly of FIG. 1A. These data may fit to aformula for SAG for a spherical conic section, e.g.,z(r)=r²/[R+(R²−r²)^(1/2)], wherein for a best sphere of radius 31.9 mm,as in an example embodiment, and a curvature of best sphere, R,corresponding to 0.03, the different actual radii of curvature, r, for asurface with aspheric departure produce SAG differences compared tovalues for a true spherical conic section. These aspherical SAGs for anexample fifteenth surface are compared with would be true spherical SAGsin Table 2 for different distances Y from the vertex center at Y=0 toY=6.25 (mm) in steps of 0.25 (mm).

The aspheric sags in Table 3 that are plotted in FIG. 2 are the asphericsag difference numbers shown in Table 2, which are the differences fromthe best fit sphere sags of the aspheric surface 15 or object facingsurface of the lens E8(A) in the example of FIG. 1A. Table 3 also showsvalues of aspheric slope that are plotted in FIG. 3.

Referring now to FIGS. 1A-8, FIG. 1A is described in detail above. FIG.1B schematically illustrates a ray trace diagram for the opticalassembly of FIG. 1A.

FIG. 2 is a plot of aspheric sag versus radial distance, or the dataprovided in the second column from the left in Table 3, for the 15^(th)optical surface from the object in the example optical assemblyillustrated schematically in FIG. 1A. The aspheric sag for the 15^(th)surface in this example has a sag maximum between 4 mm and 6 mm from thecenter of the 15^(th) lens surface. The sag has minimum values betweenapproximately −5 μm and −10 μm both at the center and at the edge about6.25 mm from the center. The sag plot has a width of approximately 2 mmat −4 μm. The sag has points of inflection at approximately 4 mm and 6mm from the center of the 15^(th) lens surface.

FIG. 3 is a plot of slope of aspheric sag versus radial distance, or thedata provided in the fourth column from the left (or rightmost column)in Table 3, for the 15^(th) optical surface in the example opticalassembly illustrated schematically in FIG. 1A. The aspheric slope has amaximum between o and 5 μm/mm between 3 mm and 5 mm from the center ofthe 15^(th) lens surface. The aspheric slope has a lowest value at theouter edge of the 15^(th) lens surface of around −15 μm/mm. The asphericslope has points of inflection between around 3 mm and 4 mm and at theedge around 6 mm from the center of the 15^(th) lens surface.

While the asphere may be disposed on other optical surfaces and/or onother lens elements in other embodiments, the 15th surface is selectedin the embodiment illustrated by example in FIG. 1A at least in part dueto the advantageous ratio of the chief ray and marginal ray heights atthat location within the optical assembly.

An image sensor, e.g., a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) device is disposed at the image planein embodiments that include an assembled compact, miniature, pointaction or point of view camera or other compact digital camera. Theoptical assembly may be configured for later assembly with an imagesensor. In this sense, the first and second optical groups may bemanufactured or assembled separately and later combined, and in general,parts of the optical assembly or point action camera may be separatelymanufactured or assembled and it is possible in certain embodiments toreplace, restore or realign optical group G1, optical group G2, opticalgroup G3 and/or certain other groups of one or more of the lenses orother optical components of the optical assembly or point action camera.

FIGS. 4A-4E respectively show plots of tangential ray aberrationsrespectively at 75°, 55°, 35°, 15° and 0° for the wide field of viewobjective assembly illustrated in FIG. 1A. FIGS. 4A-4E and 5A-5E showfive pairs of graphs, where each pair illustrates the tangential andsagittal rays at one of these five field angles. The independentvariable (horizontal axis) is the relative coordinate of a ray over thepupil diameter. The vertical axis has a maximum distance measure of+/−approximately five microns or a spread of ten microns or less over a150 degree field (which is clearly advantageous over a conventionalsystem that may have, e.g., a 20 micron spread). The vertical axistherefore represents the transverse ray aberration (ray interceptiondistance from the ideal focal point) of a ray passing through a specificrelative pupil position. Graphs 4A-4E (tangential plane) and 5A-5E(sagittal plane) show the transverse ray aberrations for an on-axis raybundle as the bundle is refracted through the lens elements of theoptical assembly of FIG. 1A.

In FIGS. 4E and 5E, the performance of the embodiment of FIG. 1A isillustrated for a ray bundle at zero degrees with the optical axis.Graphs 4D and 5D show the performance of the optical assembly of FIGS.1A-1B for a ray bundle when the light source is moved providing anincident angle of 28 degrees with the optical axis. Graphs 4C and 5Cshow the performance of the optical assembly of FIGS. 1A-1B for a raybundle when the light source is moved providing an incident angle of39.2 degrees with the optical axis. Graphs 4B and 5B show theperformance of the optical assembly of FIGS. 1A-1B for a ray bundle whenthe light source is moved providing an incident angle of 48.5 degreeswith the optical axis. Graphs 4A and 5A show the performance of theoptical assembly of FIGS. 1A-1B for a ray bundle when the light sourceis moved providing an incident angle of 56 degrees with the opticalaxis.

LCA is demonstrated in FIGS. 4A-4E as the separation of the rays whichcorrespond to five different colors or wavelengths, which are in thisexample 650 nm, 610 nm, 555 nm, 510 nm and 465 nm.

FIG. 6 illustrates the polychromatic diffraction modulation transferfunction (MTF) plots of contrast vs. spatial frequency for pixels lyingnormal to the optical axis (F1), 14 degrees from normal to the opticalaxis (F2), 28 degrees from normal to the optical axis (F3), 39.2 degreesfrom normal to the optical axis (F4), 48.5 degrees from normal to theoptical axis (F5), and 56 degrees from normal to the optical axis (F6).Those pixels lying at 56 degrees from normal to the optical axis wouldbe those near the edge of an image captured with a point action cameraassembly having a field of view of 120 degrees.

A point action camera or other compact digital camera is provided hereinhaving a wide field of view of more than 90 degrees, and may be 120degrees or more. Advantageously high areas under the curves arenoticeable in FIG. 6. In accordance with FIGS. 4A-4E, the plots of FIG.6 demonstrate that the image quality of the embodiment of FIG. 1A isadvantageous. For example, all of the plots are above 0.3, and in factabove 0.35, at 200 cycles/mm and all of the plots are above 0.5, and infact above 0.55, at 100 cycles/mm. This indicates that the opticalassembly of FIG. 1A is configured to provide images of objects withexceptional contrast so that in tandem with an image sensor havingpixels that are no larger than a few microns, e.g., 2.4 microns, highquality images can be captured.

FIG. 7 shows plots of diffraction modulation transfer function (MTF)versus defocussing position for rays incident at 0, 14, 28, 39 and 56degrees. The plots of FIG. 7 show that an advantageous depth of focus isprovided by the optical assembly of FIGS. 1A-1B that is not less than 20microns.

FIG. 8 shows astigmatic field curves for tangential (e.g., vertical) fan(T) and sagittal (e.g., horizontal) fan (S) for the optical assemblyillustrated schematically at FIG. 1A as well as the tangential fan (T′)and sagittal fan (S′) for a similar optical assembly except that thethirteenth optical surface has no aspheric departure. FIG. 8 shows thatwithout the asphere, the longitudinal astigmatism (T′−S′)˜0.75 mm inthis example. With an aspheric departure in accordance with certainembodiments, e.g., on the fifteenth surface, such as has been describedand illustrated in the example of FIGS. 1A-1B, the longitudinalastigmatism reduces to approximately zero. Moreover, the field curvatureis approximately flat, e.g., <<50 microns, across the sensor format.

An optical design in accordance with the first embodiment exhibits anadvantageous ratio of total track length to effective focal length, orTTL/EFL <12. The specific example illustrated schematically in FIG. 1Ahas a calculated TTL to EFL ratio of 11.88 in air, i.e., in physicalgeometrical units for the track and focal lengths, i.e., where the unityindex of refraction or n≈1 is used throughout in the calculation. TheTTL is less than 10 cm in certain embodiments, while EFL is generallyless than 10 mm. The example of FIG. 1A has TTL=85 mm and EFL=7.1 mm.This example ratio can also be calculated optically by taking intoaccount the indices of refraction of the glasses, polymers and/or othersolid, liquid and/or gaseous materials of the cover plate element. Whenthe TTL/EFL ratio is calculated optically as an optical track lengthover an optical focal length that takes into account the index ofrefraction of the material that forms the cover glass element (otherwisesometimes deemed part of a separate image sensor component to be coupledto the optical assembly), then the ratio is calculated to beapproximately 11.94.

An effective focal length of the first group G1 that includes the firsttwo lens elements E1 and E2 may be between approximately −5 and −20, orbetween −7 and −16, or between −9 and −14, or approximately −11, orapproximately −12 or −11.3. The lens Group G2 including the lenses E3-E5may have an effective focal length between +10 and +25, or between +12and +23, or between +14 and +21, or between +16 and +19 or around +17 oraround +18 or +17.2.

In this context, referring again to Table 1, which generally disclosescertain specifications of the example optical assembly that isrepresented schematically in side view in FIG. 1A, Table 1 lists radiusof curvature (RDY) values for each of the optical surfaces, i.e.,numbered 1-10 and 12-19 in the left hand column of Table 1, of the eightlens elements including ten lenses E1-E10 that make up the first, secondand third optical groups G1, G2, G3. Table 1 also lists thickness values(THI) for each of the lens elements and spacings between the lenselements, or the distances between each adjacent optical surface in theoptical assembly illustrated schematically in side view in FIG. 1A.

Referring to the example illustrated schematically in FIGS. 9A-9B, andin the plots shown in FIGS. 10-18, and quantitatively at Tables 4-6, anoptical assembly in accordance with certain embodiments may include afirst lens group G1, a second lens group G2, a third lens group G3 and afourth lens group G4. The first lens group G1 is disposed nearer to theobject or scene that is being imaged than the second lens group G2. Thesecond lens group G2 is disposed between the first lens group G1 and thethird lens group G3. The third lens group is disposed between the secondlens group G2 and the fourth lens group G4. The image plane lies justbeyond the fourth lens group G4. Together, the first, second, third, andfourth optical groups G1, G2, G3 and G4, respectively, cover a widefield of view, i.e., greater than 120 degrees, or in certain embodimentgreater than 135 degrees and in others greater than 150 degrees and evenin certain embodiments significantly close to 180 degrees.Alternatively, there may be two, or three, or five or more lens groupsinstead of four, or the entire optical assembly may form a single lensgroup.

Generally speaking, the lens group G1 is configured to collect widefield rays and reduce the field angle to groups G2 and G3. The group G2is configured to provide advantageously low axial chromatic aberrationand spherochromatism or variation of spherical with wavelength. Thearrangement of G2 and G3 about the aperture stop advantageously balancesfield aberrations of multiple orders. The placement and configuration ofthe asphere E7(A) advantageously corrects higher order astigmatism.

The lens groups G2 and G3 are configured such that the optical assemblyproduces advantageously low imaging errors from aberrations, andparticularly distortion and astigmatism. However, the configuration caninclude contributions within the second lens group G2 to the collectionand reduction of wide field rays and/or contributions within the firstlens group G1 and/or fourth lens group G4 to the correction ofaberrations such as distortion and astigmatism. For example, one or morelens elements of the group G2 may have a material or shapecharacteristic tending to facilitate collection of wide angle raysand/or a surface of one or more lens elements of group G1 and/or G4 mayhave aspheric departure or another characteristic configured to assistin the correction of aberrations.

In the embodiment illustrated schematically at FIGS. 9A-9B, the firstlens group G1 includes two singlet lenses and a doublet, from furthestto closest to the image plane, namely lens E1, and lens E2 and lensesE3/E4 form the doublet. Lens E1 comprises a convexo-concave lens, ormeniscus, in the example embodiment of FIGS. 9A-9B. This means that theobject facing surface of lens E1, which is the first surface of theoptical assembly of the example embodiment of FIGS. 9A-9B, has a convexshape tending to converge incident light, while the image facing surfaceof lens E1, which is the second surface of the optical assembly of FIGS.9A-9B, has a concave shape tending to diverge incident light. The lensE1 has a nominal overall optical power. This lens E1 may have anextended radius outside of an active radius which assists andfacilitates a wide field of view feature of the optical assembly ofFIGS. 9A-9B. The physical dimensional characteristics of the lenses ofthe optical assemblies of the embodiments described herein generallypermit configuring the wide field of view optical assembly within a lensbarrel of a point action camera and/or within a compact or miniaturepoint action camera.

The lens E1 may be fixed, i.e., relative to the image plane and otherfixed elements of the system. Alternatively, the lens E1 may be movableto permit focusing by automatic or manual actuation using, e.g., a voicecoil motor, piezo, or MEMS coupled to the lens E1. In this alternativeembodiment, a feedback based on analysis of image data received at theimage sensor by a processor, an image processor or an image signalprocessor (ISP). Another optical group may include one or more movablelenses, mirrors or other optics. In this context, a zoom feature mayalso be provided optically and/or electronically. Thus, embodiments ofpoint action cameras described herein include fixed focus, autofocus andautofocus zoom point action cameras. In certain embodiments, the lens E1has an index of refraction at the sodium d line (i.e., 587.5618 nm) ataround 1.88, or n(λd)≈1.9. The dispersion may be around 41. The lens E1has little overall optical power, as mentioned, and serves primarily asa collecting lens that facilitates the wide field of view of the opticalassembly.

Lens E1 has a larger diameter in order to collect rays at outer edges ofthe wide field of view and reduces the field angle for the subsequentlenses of the optical assembly. Lens group G1, and particularly lensesE1 and E2, generally serves to reduce the ray angle for the group G2 andG3 lens elements. Lens groups G2 and G3 generally serve to balance orcorrect field aberrations of multiple orders, including distortion andastigmatism errors. The overall optical design of the lens groups G2 andG3 generally serves to correct distortion, while the aspheric twelfthsurface of the optical assembly of FIGS. 9A-9B generally serves tocorrect higher order astigmatism.

The lens element E2 of the lens group G1 has a biconcave structure inthe example of FIGS. 9A-9B. In other words the object facing surface ofthe lens E2, which is the third surface of the optical assembly of FIGS.9A-9B, has a concave shape, while the image facing surface of the lensE2, or the fourth surface of the optical assembly of FIGS. 9A-9B, alsohas a concave shape tending to diverge incident light rays. The lens E2has a negative overall focal length and serves as a diverging opticalelement. In certain embodiments, the lens E2 has an index of refractionat the sodium d line (i.e., 587.5618 nm) at around 1.5, or n(λd)≈1.5.The dispersion may be around 82.

The lens elements E3/E4 form a doublet, such that lenses E3 and E4 andphysically attached. Only the object facing surface of E3 and the imagefacing surface of E4 are indicated in Table 1 as the slightly concavefifth optical surface and the slightly convex sixth optical surface ofthe optical assembly. The lens E3 has an index of refraction around 1.5and a dispersion around 82, while the lens E4 has an index of refractionaround 1.74 and a dispersion around 32.

The lens group G1 has an overall negative focal length, e.g., in oneembodiment EFL (G1)≈−11.5 mm, and serves to collect and convergeincoming light from an object, group of objects or a foreground,background or overall scene, including a wide field of view greater than90 degrees in the horizontal and/or vertical dimensions, and typically120, 135, or 150 degrees or more in the horizontal and/or 110-120degrees or more in the vertical. The rays received from the opticalgroup G1 are further optically reduced by optical group G2, which has apositive focal length, e.g., in one embodiment EFL (G2)≈37.2 mm. Opticalgroup G2 serves to correct aberrations such as distortion before imagesare captured by an image sensor of a point action camera for viewing ona display, and/or for recording or storage or for data analysis,monitoring, security or surveillance and/or for transmission and/orimage processing.

The optical group G2 in the example of FIGS. 9A-9B includes a doublet.Lenses E5 and E6 are attached. Lens E5 has an index of refraction around81 and a dispersion around 23, while lens E6 has an index of refractionaround 62 and a dispersion around 63. The object facing surface of E5 isconvex and the image facing surface of E6 is convex, such that the E5/E6doublet has a strong positive focal length, which in the illustratedexample of FIGS. 9A-9B is 37.2 mm.

An aperture stop is disposed between the E5/E6 doublet of the secondoptical group G2 and the aspheric lens element E7(A) of the thirdoptical group G3. Alternatively, an aperture stop may be disposedbetween the lens groups G1 and G2, whatever number of optical elementseach may comprise. An aperture stop may be located differently and theremay be one or more additional apertures within the optical assembly.

The third optical group also includes a doublet including attachedlenses E8 and E9. In certain embodiments, the image facing surface oflens E8 and the object facing surface of the lens E9 are in directcontact. An adhesive or other standard process of coupling constituentlenses of a doublet may be used, which process may depend upon thematerials of the constituent lenses E8 and E9. In certain embodiments,the lens E8 has an index of refraction at the sodium d line (i.e.,587.5618 nm) at around 1.76, or n(λd)≈1.76. The dispersion of lens E8may be around 26. In certain embodiments, the lens E9 has n(λd)≈1.62. Incertain embodiments, the lens E9 has a dispersion around 63. The E8/E9doublet overall serves to configure the light rays before becomingincident upon the lens element E10 of the fourth lens group G4.

Referring to FIGS. 9A-9B, there a significant advantage to having anoptical assembly in accordance with certain embodiments, wherein theE8/E9 doublet, which is shown disposed between the asphere E7(A) and thesinglet E10 in FIGS. 9A-9B, is configured to correct obliqueaberrations.

The lens element E7(A) has a concavo-convex shape. The object facingsurface of the lens E7(A), which is the twelfth surface of the opticalassembly of FIGS. 9A-9B, has a concave shape which converges incidentlight. The twelfth surface of the optical assembly of FIGS. 9A-9B alsohas a significant aspheric departure in this example embodiment. Theobject facing surface of the lens E7(A), which is the twelfth surface ofthe optical assembly of FIGS. 9A-9B, has a concave shape, while theimage facing thirteenth surface has a convex shape. In certainembodiments, the lens E7(A) has an index of refraction at the sodium dline (i.e., 587.5618 nm) at around 1.5, or n(λd)≈1.5. The dispersion ofthe lens E8(A) may be around 82. Table 1 indicates certain asphericparameters for the lens element E7(A).

After the doublet E8/E9 of the third optical group G3, there are twosinglets E10 and E11 each of the fourth optical group G4. Each of lensesE10 and E11 has a convexo-quasi planar or convexo-concave shape. Incertain embodiments, the lens E10 has an index of refraction at thesodium d line (i.e., 587.5618 nm) at around 1.62, or n(λd)≈1.62. Thedispersion of lens E10 may be around 63. In certain embodiments, thelens E10 has n(λd)≈1.62. In certain embodiments, the lens E10 has adispersion around 63. The fourth optical group G4 serves to deliver atelecentric cone to the image sensor.

Between the twentieth surface of the optical assembly of FIGS. 9A-9B andthe image plane are an IR filter and a cover plate. The IR filter servesto cut out infrared light that can otherwise interfere with the functionof a silicon-based image sensor to collect visible image data. Incertain embodiments, the IR filter is disposed within a same housing asthe optical assembly or the groups G2, G3 and G4 if the group G1 isseparately packaged or the groups G3 and G4 if groups G1 and G2 areseparately packaged. The cover plate serves to protect the image sensorfrom incident dust, water, oxygen or other corrosive or artifactproducing elements that may be present in the ambient space surroundingthe point action camera. A separate baffle may be included to reduce theamount of stray light that may become otherwise incident upon the imagesensor. Each of the IR filter and the cover glass may have a refractiveindex around 1.5 and a dispersion around 64. For example, NBK7 Schottglass may be used.

The aspheric departure of the twelfth optical surface of the opticalassembly in the example embodiment of FIGS. 9A-9B serves toadvantageously significantly reduce higher order astigmatism errors thatwould be otherwise inherent in a wide field of view system without anaspheric surface in accordance with embodiments described herein.Moreover, the advantageous design of the optical assembly of FIGS.9A-9B, and specifically of the second and third optical groups G2 andG3, and more specifically of the aspheric lens element E7(A), and stillmore specifically of the aspheric object facing surface of the lenselement E7(A) permits the optical assembly in this embodiment to have amore efficient manufacturability than conventional designs that containmultiple aspheric surfaces and/or multiple aspheric lenses or otheroptical elements.

FIGS. 9A-9B has H(θ)/f*θ=1.078. In another similar embodimentH(θ)/f*θ=1.174. In other embodiments, H(θ)/f*θ is greater than 1.2, 1.3,1.4 and even 1.5, and in other embodiments H(θ)/f*θ is approximately 1.

Table 1 generally discloses certain specifications of the exampleoptical assembly that is represented schematically in side view in FIG.9A. Table 4 lists RDY, which is the radius of curvature of the opticalsurface. Table 4 also lists THI which are the thicknesses of the lensesE1-E10 and the spaces between the lenses E1-E10 in sequential order. Therow 1 thickness describes the thickness of the first lens E1 in thisembodiment. The row 2 thickness describes the thickness of the spacingbetween the first lens E1 and second lens E2. The spacing may includeair, or for example dry air or nitrogen gas or vacuum or a noble gas, ora liquid such as water. The row 3 describes the thickness of the secondlens E2. The row 4 describes the air spacing between the second lens E2and the object facing surface of the E3/E4 doublet in this example. Therow 5 describes the thickness of the third lens E3. The row 6 describesthe thickness of the fourth lens E4. There is no spacing between E3 andE4 in this example. The row 7 describes the thickness of the spacingbetween E3/E4 doublet and the E5/E6 doublet in this example. The row 8describes the thickness of the lens E5 and the row 9 describes thethickness of the lens E6. The row 10 describes the thickness of thespacing between the doublet E5/E6 and the aperture stop. The row 11(STO) describes the thickness of the spacing between the aperture stopand the lens element E7(A). The row 12 describes the thickness of theaspheric lens element E7(A). The aspheric coefficients A-E for theeighth lens E8(A) are provided just below the row 15. The asphericequation is provided at the top of Table 2. The row 13 describes thethickness of the spacing between E7(A) and the E8/E9 doublet. There isno spacing between the lenses E8 and E9 in this example wherein the lenselement E8/E9 is a doublet. The row 14 describes the thickness of thelens E8, while the row 15 describes the thickness of the lens E9. Therow 16 describes the thickness of the spacing between the E8/E9 doubletand the lens E10. The row 17 describes the thickness of the lens E10.The row 18 describes the thickness of the spacing between E10 and E11.The row 19 describes the thickness of the lens E11. The row 20 describesthe thickness of the spacing between E11 and the IR cut filter. The row21 describes the thickness of the IR cut filter. The row 22 describesthe spacing between the IR cut filter and the sensor cover glass. Therow 23 describes the thickness of the sensor cover glass. The row 24describes the thickness of the spacing between the sensor cover glassand the image plane. Eight lens elements including five singlets andthree doublets, or eleven lenses E1-E11 make up the example opticalassembly that is illustrated schematically at FIG. 9A, while a pointaction camera or other compact digital camera includes the IR cutfilter, cover glass and an image sensor packaged within a housing alongwith the optical assembly. The first two lenses E1-E2 and the doubletE3/E4 form a first optical group G1, the E5/E6 doublet forms the secondoptical group G2, the E7(A) singlet and E8/E9 doublet form the thirdoptical group G3, and the final two lens elements E10 and E11 form thefourth optical group G4.

The radii of curvature are, in the single aspheric surface example,approximately, i.e., within manufacturing tolerances, the sameeverywhere along the optical surface for each of the first througheleventh and thirteenth through nineteenth surfaces of the opticalassembly of FIG. 9A. In Table 4, the row 6 describes the curvature ofboth the sixth and seventh surfaces, which are the image facing surfaceof the lens E3 and the object facing surface of the lens E4, which havethe same curvature. Likewise, the row 9 in Table 4 describes thecurvature of both the tenth and eleventh surfaces, which are the imagefacing surface of the lens E5 and the object facing surface of the lensE6, which have the same curvature. Also, the row 15 in Table 4 describesthe curvature of both the fifteenth and sixteenth surfaces, which arethe image facing surface of the lens E8 and the object facing surface ofthe lens E9, which have the same curvature. That is, the coefficients Athru E are each approximately zero for 21 out of 22 surfaces of theembodiment of FIG. 9A in the single aspheric surface example of a widefield of view optical assembly for a point action camera or compactcamera, or miniature camera module or other camera or camera moduleincluding a single aspheric lens element, or only one aspheric lenselement, and exhibiting advantageously low distortion and lowastigmatism, as well as high MTF at Nyquist and half Nyquistfrequencies, and low lateral chromatic aberration, and compactness inthree spatial dimensions. The departures from spherical of the twelfthsurface are represented in Table 4 as nonzero coefficients A-C, whichcorrespond mathematically to the coefficients indicated in the formulathat is provided above the Table 2 in the illustration (where D=0 andE=0 in this example).

This formula with the non-zero coefficients A-C as indicated in Table 4represent the aspheric curvature of the surface 12 or object facingsurface of the lens E7(A) of the example optical assembly that isillustrated schematically in FIG. 9A.

The specification data of Table 4 represent the first order softwareinputs to complete the optical model. FNO is F number and isapproximately 2.4 in this example. DIM is the dimension which is mm. WLare the wavelengths which are in nanometers, and are 650 nm (red), 610nm (orange), 555 nm (yellow), 510 nm (green) and 465 nm (blue) in thisexample.

Table 5 shows aspherical and spherical SAG data for the twelfth surfaceof the optical assembly of FIG. 9A, or the object facing surface of lensE7(A). These aspherical SAGs for an example twelfth surface are comparedwith would be true spherical SAGs in Table 5 for different distances Yfrom the vertex center at Y=0 to Y=3.5 (mm) in steps of 0.14 (mm).

The aspheric sags in Table 6 that are plotted in FIG. 10 are theaspheric sag difference numbers shown in Table 5, which are thedifferences from the best fit sphere sags of the aspheric surface 12 orobject facing surface of the lens E7(A) in the example of FIG. 9A. Table6 also shows values of aspheric sag slope that are plotted in FIG. 11.

Referring now to FIGS. 9A-18, FIG. 9A is described in detail above. FIG.9B schematically illustrates a ray trace diagram for the opticalassembly of FIG. 9A. FIG. 10 is a plot of aspheric sag versus radialdistance, or the data provided in the second column from the left inTable 6, for the 12th optical surface from the object in the exampleoptical assembly illustrated schematically in FIG. 9A. The aspheric sagfor the 12th surface in this example has a sag maximum between 2 mm and3 mm from the center of the 12th lens surface. The sag has minimumvalues between approximately −10 μm and −12 μm both at the center and atthe edge about 3.5 mm from the center. The sag plot has a width ofapproximately 3.5 mm at −6 μm. The sag has a point of inflection atapproximately 1.5 mm from the center of the 12th lens surface.

FIG. 11 is a plot of slope of aspheric sag versus radial distance, orthe data provided in the fourth column from the left (or rightmostcolumn) in Table 6, for the 12th optical surface in the example opticalassembly illustrated schematically in FIG. 9A. The aspheric sag slopehas a minimum around 1.5 mm from the center of the 12^(th) lens surfacebetween −5 μm/mm and −10 μm/mm. The aspheric sag slope has a highestvalue at the outer edge of the 12th lens surface of around 23 μm/mm. Theaspheric slope has a point of inflection between around 0.5 mm and 1 mmfrom the center of the 12th lens surface.

While the asphere may be disposed on other optical surfaces and/or onother lens elements in other embodiments, the 12th surface is selectedin the embodiment illustrated by example in FIG. 9A at least in part dueto the advantageous ratio of the chief ray and marginal ray heights atthat location within the optical assembly.

An image sensor, e.g., a charge coupled device (CCD) or a complementarymetal oxide semiconductor (CMOS) device is disposed at the image planein embodiments that include an assembled compact, miniature, pointaction or point of view camera or other compact digital camera. Theoptical assembly may be configured for later assembly with an imagesensor. In this sense, the first and second optical groups may bemanufactured or assembled separately and later combined, and in general,parts of the optical assembly or point action camera may be separatelymanufactured or assembled and it is possible in certain embodiments toreplace, restore or realign optical group G1, optical group G2, opticalgroup G3 and/or certain other groups of one or more of the lenses orother optical components of the optical assembly or point action camera.

FIGS. 12A-12D respectively show plots of tangential ray aberrationsrespectively at 56°, 39.2°, 28° and 0° for the wide field of viewobjective assembly illustrated in FIG. 9A. FIGS. 12A-12D and 13A-13Dshow four pairs of graphs, where each pair illustrates the tangentialand sagittal rays at one of these four field angles. The independentvariable (horizontal axis) is the relative coordinate of a ray over thepupil diameter. The vertical axis has a maximum distance measure of+/−approximately five microns or a spread of ten microns or less over a120 degree field (which is clearly advantageous over a conventionalsystem that may have, e.g., a 20 micron spread). The vertical axistherefore represents the transverse ray aberration (ray interceptiondistance from the ideal focal point) of a ray passing through a specificrelative pupil position. Graphs 12A-12D (tangential plane) and 13A-13D(sagittal plane) show the transverse ray aberrations for an on-axis raybundle as the bundle is refracted through the lens elements of theoptical assembly of FIG. 9A.

In FIGS. 12D and 13D, the performance of the embodiment of FIG. 9A isillustrated for a ray bundle at zero degrees with the optical axis.Graphs 12C and 13C show the performance of the optical assembly of FIGS.9A-9B for a ray bundle when the light source is moved providing anincident angle of 28 degrees with the optical axis. Graphs 12B and 13Bshow the performance of the optical assembly of FIGS. 9A-9B for a raybundle when the light source is moved providing an incident angle of39.2 degrees with the optical axis. Graphs 12A and 13A show theperformance of the optical assembly of FIGS. 9A-9B for a ray bundle whenthe light source is moved providing an incident angle of 56 degrees withthe optical axis. LCA is demonstrated in FIGS. 12A-12D as the separationof the rays which correspond to five different colors or wavelengths,which are in this example 650 nm, 610 nm, 555 nm, 510 nm and 465 nm.

FIG. 14 illustrates the polychromatic diffraction modulation transferfunction (MTF) plots of contrast vs. spatial frequency for pixels lyingnormal to the optical axis (F1), 14 degrees from normal to the opticalaxis (F2), 28 degrees from normal to the optical axis (F3), 39.2 degreesfrom normal to the optical axis (F4), 48.5 degrees from normal to theoptical axis (F5), and 56 degrees from normal to the optical axis (F6).Those pixels lying at 56 degrees from normal to the optical axis wouldbe those near the edge of an image captured with a point action or othercompact digital camera assembly having a field of view of 120 degrees.

A point action camera or other compact digital camera is provided hereinhaving a wide field of view of more than 90 degrees, and may be 120degrees or more. Advantageously high areas under the curves arenoticeable in FIG. 14. In accordance with FIGS. 12A-12D, the plots ofFIG. 14 demonstrate that the image quality of the embodiment of FIG. 9Ais advantageous. For example, all of the plots are above 0.3 at 200cycles/mm and all of the plots are above 0.6 at 100 cycles/mm. Thisindicates that the optical assembly of FIG. 9A is configured to provideimages of objects with exceptional contrast so that in tandem with animage sensor having pixels that are no larger than a few microns, e.g.,2.4 microns, high quality images can be captured.

FIG. 15 shows plots of diffraction modulation transfer function (MTF)versus defocussing position for rays incident at 0, 14, 28, 39 and 56degrees. The plots of FIG. 15 show that an advantageous depth of focusis provided by the optical assembly of FIGS. 9A-9B that is greater than20 microns.

FIG. 16 shows astigmatic field curves for tangential (e.g., vertical)fan (T) and sagittal (e.g., horizontal) fan (S) for the optical assemblyillustrated schematically at FIG. 9A as well as the tangential fan (T′)and sagittal fan (S′) for a similar optical assembly except that thetwelfth optical surface has no aspheric departure. FIG. 16 shows thatwithout the asphere, the longitudinal astigmatism (T′−S′)˜0.75 mm inthis example. With an aspheric departure in accordance with certainembodiments, e.g., on the twelfth surface, such as has been describedand illustrated in the example of FIGS. 9A-9B, the longitudinalastigmatism reduces to approximately zero. Moreover, the field curvatureis approximately flat, e.g., <<50 microns, across the sensor format.

An optical design in accordance with the second embodiment exhibits anadvantageous ratio of total track length to effective focal length, orTTL/EFL <8. The specific example illustrated schematically in FIG. 9Ahas a calculated TTL to EFL ratio of 8 in air, i.e., in physicalgeometrical units for the track and focal lengths, i.e., where the unityindex of refraction or n≈1 is used throughout in the calculation. TheTTL is less than 8 cm in certain embodiments, while EFL is generallyless than 10 mm. The example of FIG. 9A has TTL=55 mm and EFL=7.12 mm.This example ratio can also be calculated optically by taking intoaccount the indices of refraction of the glasses, polymers and/or othersolid, liquid and/or gaseous materials of the cover plate element.

The example embodiment of FIG. 9A also features high performance withregard to suppression of stray light. High dynamic range (HDR) isachieved in the example of FIG. 9A because stray light is suppressed.Stray light can be caused by two surface ghosts (double bounce ghostsfrom lens surface), ghosting originating from sensor and subsequentreflections from lens surface back to sensor (“sensor sees itself”),scattered light from mechanical structure, and scattered light fromedges of lens elements. Stray light contributions are suppressed viadesign process by minimizing the number and location of near normalincidence surfaces (e.g., angle of incidence or refractive is −0degrees). The embodiment of FIG. 9A has 90% or more of return ghostsfoci more than +/−2 mm from image sensor plane.

FIG. 17 is a plot of irradiance ratio versus angle, where

${{Irradiance}\mspace{14mu}{ratio}} = \frac{{Stray}\mspace{14mu}{light}\mspace{14mu}{peak}\mspace{14mu}{irradiance}}{0{^\circ}\mspace{14mu}{in}\text{-}{field}\mspace{14mu}{peak}\mspace{14mu}{irradiance}}$The irradiance ratio is significantly below 1/10,000, and isapproximately 1/100,000.

FIG. 18 is a plot of power ratio versus angle, where

${{Power}\mspace{14mu}{ratio}} = \frac{{Stray}\mspace{14mu}{light}\mspace{14mu}{total}\mspace{14mu}{power}}{0{^\circ}\mspace{14mu}{in}\text{-}{field}\mspace{14mu}{total}\mspace{14mu}{power}}$The power ratio is significantly below 1/100, and is approximately1/1000.

General Discussion

Yet greater dynamic capacities in the process of building a point actioncamera with both wide field of view and heretofore unknown reduction indistortion, astigmatism and combinations of these optical aberrationsthat have been otherwise problematic in conventional wide field of viewsystems is provided herein with optical assemblies in accordance withmultiple embodiments that contain only one aspheric lens element, e.g,lens element E8(A) of the example of FIG. 1A or lens element E7(A) ofthe example of FIG. 9A in combination with five or six other lenselements that have spherical curvatures to understood tolerances. One orboth surfaces of the single aspheric lens element of these embodimentsmay have significant calculated aspheric departure, while the other lenselements are spheres (or in other embodiments cylinders or a combinationof cylinders and spheres).

Example embodiments have been provided above wherein only one opticalsurface within the optical assembly has a specifically-intended andadvantageous aspheric departure. In the embodiments illustratedschematically in side view in FIGS. 1A and 9A, five or six lenselements, when the doublets are characterized as single lens elements,do not have departures from spherical (i.e., at least none that exceedspecified optical tolerances).

In another set of embodiments, one or more aspheric lens element is/areprovided in the first lens Group G1. For example, lens element E1 and/orE2 may have one or more surfaces with aspheric departures that serve toreduce astigmatism in a wide field of view point action camera systemthat is also or already configured with significantly reduced distortioncharacteristics, particularly at the edges of the field of view (e.g.,50°, 55°, 60°, 65°, 70°, or 75° or more from normal to the opticalaxis), where conventional uncorrected wide field of view systems tend toexhibit unacceptably high combinations of either or both of distortionaland astigmatic aberrations. In certain embodiments, only lens element E1or lens element E2 has one or both surfaces that exhibit calculablyadvantageous aspheric departures.

In specific embodiments, only a single surface, e.g., the 1st, 2nd, 3rdor 4th surface, of the optical assembly has aspheric departure thatprovides a point action camera with a wide field of view along withunprecedented reductions in distortional, astigmatic or combinationalaberrations that would be otherwise inherent in less thorough designs,in designs without any aspheric surface or surfaces and/or in designswithout the specific optical design shape and/or aberrational errorcorrectional characteristics provided herein. In a specific alternativeembodiment, only the first lens surface of the optical assembly, or thesurface of lens E1 that faces the object, includes demonstratedly andadvantageously significant aspheric departure. In another embodiment,the image facing surface of lens E1 has a uniquely asphericalattributional curvature characteristic within the optical assembly of awide field of view point action camera.

Alternative embodiments have a single aspheric surface within the lensgroup G2 at the tenth lens surface or image facing surface of the lensE6 (or E6(A) in this alternative embodiment) which is the image-sidelens of the doublet E5/E6. Another alternative to having asphericdeparture on the twelfth surface, as in the illustrated example of FIG.9A, or on the fifteenth surface, as in the illustrated example of FIG.1A, is to instead provide aspheric curvature on the fourteenth lenssurface, which is the object facing surface of the lens E8(A) in theFIG. 9A example, and is the image facing surface of the lens E7(A) inthe FIG. 1A example. Other surfaces of the lens groups G2 and G3 couldalso have aspheric departures that could benefit, albeit to a lesserextent than the aforementioned optical surfaces primarily of lens groupG3, the versatility and optical design characteristics of an opticalassembly of a point action camera.

While an exemplary drawings and specific embodiments of the presentinvention have been described and illustrated, it is to be understoodthat that the scope of the present invention is not to be limited to theparticular embodiments discussed. Thus, the embodiments shall beregarded as illustrative rather than restrictive, and it should beunderstood that variations may be made in those embodiments by workersskilled in the arts without departing from the scope of the presentinvention.

In addition, in methods that may be performed according to preferredembodiments herein and that may have been described above, theoperations have been described in selected typographical sequences.However, the sequences have been selected and so ordered fortypographical convenience and are not intended to imply any particularorder for performing the operations, except for those where a particularorder may be expressly set forth or where those of ordinary skill in theart may deem a particular order to be necessary.

A group of items linked with the conjunction “and” in the abovespecification should not be read as requiring that each and every one ofthose items be present in the grouping in accordance with allembodiments of that grouping, as various embodiments will have one ormore of those elements replaced with one or more others. Furthermore,although items, elements or components of the invention may be describedor claimed in the singular, the plural is contemplated to be within thescope thereof unless limitation to the singular is explicitly stated orclearly understood as necessary by those of ordinary skill in the art.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other such as phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “assembly” does not imply that the components or functionalitydescribed or claimed as part of the assembly are all configured in acommon package. Indeed, any or all of the various components of aassembly, e.g., optical group 1 and optical group 2, may be combined ina single package or separately maintained and may further bemanufactured, assembled or distributed at or through multiple locations.

Different materials may be used to form the lenses of the opticalassemblies of the several embodiments. For example, various kinds ofglass and/or transparent plastic or polymeric materials may be used.Examples include polyimides. Among the polymeric materials are highrefractive index polymers, or HRIPs, with refractive indices typicallyabove 1.5 (see, e.g., Hung-Ju Yen and Guey-Sheng Liou (2010). “A facileapproach towards optically isotropic, colorless, and thermoplasticpolyimidothioethers with high refractive index”. J. Mater. Chem. 20(20): 4080; H. Althues, J. Henle and S. Kaskel (2007). “Functionalinorganic nanofillers for transparent polymers”. Chem. Soc. Rev. 9 (49):1454-65; Akhmad Herman Yuwono, Binghai Liu, Junmin Xue, John Wang,Hendry Izaac Elim, Wei Ji, Ying Li and Timothy John White (2004).“Controlling the crystallinity and nonlinear optical properties oftransparent TiO₂-PMMA nanohybrids”. J. Mater. Chem. 14 (20): 2978;Naoaki Suzuki, Yasuo Tomita, Kentaroh Ohmori, Motohiko Hidaka andKatsumi Chikama (2006). “Highly transparent ZrO2 nanoparticle-dispersedacrylate photopolymers for volume holographic recording”. Opt. Express14 (26): 012712, which are incorporated by reference).

Optical image stabilization techniques may be included in a point actioncamera in accordance with certain embodiments. For examples, techniquesdescribed at U.S. Pat. Nos. 8,649,628, 8,649,627, 8,417,055, 8,351,726,8,264,576, 8,212,882, 8,593,542, 8,509,496, 8,363,085, 8,330,831,8,648,959, 8,637,961, 8,587,666, 8,604,663, 8,521,017, 8,508,652,8,358,925, 8,264,576, 8,199,222, 8,135,184 and 8,184,967, and USpublished patent applications nos. 2012/0121243, 2012/0207347,2012/0206618, 2013/0258140, 2013/0201392, 2013/0077945, 2013/0076919,2013/0070126, 2012/0019613, 2012/0120283, and 2013/0075237 which arehereby incorporated by reference, may be used.

Additionally, the various embodiments set forth herein are described interms of exemplary schematic diagrams and other illustrations. As willbe apparent to one of ordinary skill in the art after reading thisdocument, the illustrated embodiments and their various alternatives maybe implemented without confinement to the illustrated examples. Forexample, schematic diagrams and their accompanying description shouldnot be construed as mandating a particular architecture orconfiguration.

Point action cameras in accordance with several further embodiments aredescribed herein. Several examples of point action cameras that can beefficiently manufactured are illustrated in the text with reference toaccompanying drawings. Certain optical parts of the point action camerasuch as one or more lenses, mirrors and/or apertures, a shutter, ahousing or barrel for holding certain optics, a lens or a lens barrel,or other optic such as a mirror, light source, secondary sensor,accelerometer, gyroscope, power connection, a data storage chip, amicroprocessor, a wired or wireless transmission/reception connectionand/or receiver/transmitter, or housing alignment and/or coupling pinsor recesses or other such structures may be included in certainembodiments even if they have not been specifically described orillustrated herein. It is noted that in certain embodiments, a shutteris included, while in other embodiments, the point action camera doesnot have a shutter. A flash may or may not be included in any of thesecamera embodiments.

In certain embodiments, a wide field of view is desired in only a singledimension. In such cases, the principles described herein can be reducedto cylindrical applications of any of the spherical examples provided.

In addition, all references cited above and below herein, as well as thebackground, invention summary, abstract and brief description of thedrawings, are all incorporated by reference into the detaileddescription of the preferred embodiments as disclosing alternativeembodiments. Several embodiments of point action cameras have beendescribed herein and schematically illustrated by way of examplephysical, electronic and optical architectures. Other point actioncamera embodiments and embodiments of features and components of pointaction cameras that may be included within alternative embodiments, maybe described at one or a combination of U.S. Pat. Nos. 7,224,056,7,683,468, 7,936,062, 7,935,568, 7,927,070, 7,858,445, 7,807,508,7,569,424, 7,449,779, 7,443,597, 7,449,779, 7,768,574, 7,593,636,7,566,853, 7,858,445, 7,936,062, 8,005,268, 8,014,662, 8,090,252,8,004,780, 8,119,516, 8,873,167, 7,920,163, 7,747,155, 7,368,695,7,095,054, 6,888,168, 6,844,991, 6,583,444, and/or 5,882,221, and/or USpublished patent applications nos. 2013/0270419, 2013/0258140,2014/0028887, 2014/0043525, 2012/0063761, 2011/0317013, 2011/0255182,2011/0274423, 2010/0053407, 2009/0212381, 2009/0023249, 2008/0296,717,2008/0099907, 2008/0099900, 2008/0029879, 2007/0190747, 2007/0190691,2007/0145564, 2007/0138644, 2007/0096312, 2007/0096311, 2007/0096295,2005/0095835, 2005/0087861, 2005/0085016, 2005/0082654, 2005/0082653,and/or 2005/0067688. All of these patents and published patentapplications are incorporated by reference.

U.S. Pat. Nos. 7,593,636, 7,768,574, 7,807,508 and 7,244,056 which areincorporated by reference describe examples of structures where theelectrical height of a camera device is nested within the optical heightto decrease the physical height. An advantageously compact point actioncamera is provided herein in alternative embodiments. Point actioncameras that have an advantageously low ratio of optical length (orphysical size or height) to effective focal length, or TTL/EFL, areprovided herein. In specifically described examples, optical assemblieswith TTL/EFL ratios below 8.0 are provided.

US2013/0242080 which is also incorporated by reference describesexamples of point action cameras or camera modules disposed withinwatertight compartments. A mechanism may be provided for optical and/orelectrical communication of image data that does not involve breakingthe watertight seal of the housing within which the point action cameraresides.

What is claimed is:
 1. A digital point action camera, comprising anoptical assembly for a point action camera having a wide field of view,comprising multiple lens elements, including one or more aspheric lenssurfaces, configured to provide a field of view in excess of 120degrees; and an image sensor disposed approximately at a focal plane ofthe optical assembly; and a digital camera housing including electronicsand a user interface, and containing said optical assembly and saidimage sensor in optically effective relative disposition; and whereinthe optical assembly comprises, from object end to image end: a firstoptical group including two lens elements configured to collect andreduce a field angle of light incident at said wide field of view; asecond optical group, including three lens elements; and a third opticalgroup including two doublets and a singlet disposed between the twodoublets, and an aperture stop between said second and third opticalgroups, and wherein said singlet of said third optical group includes anaspheric surface that is configured to compensate higher orderastigmatism, and wherein said digital camera comprises a MTF at 200lp/mm above 0.35 and a MTF at 100 lp/mm above 0.55.
 2. The digitalcamera of claim 1, wherein a ratio of a diameter of a first lens elementat the object end of the optical assembly to an image diagonal is lessthan approximately
 3. 3. The digital camera of claim 1, wherein adiameter of a first lens element at the object end of the opticalassembly; is less than 30 mm.
 4. The digital camera of claim 1,comprising less than five microns of lateral chromatic aberration. 5.The digital camera of claim 1, comprising a ratio of total track length,from the object end of the optical assembly to the focal plane, toeffective focal length of the optical assembly (hereinafter “TTL/EFL”)that is less than
 12. 6. The digital camera of claim 1, wherein a totaltrack length TTL, from the object end of the optical assembly to thefocal plane, is less than 10 cm.
 7. The digital camera of claim 1,wherein the second group comprises a positive focal length in a rangebetween 10 mm and 25 mm.
 8. The digital camera of claim 1, wherein thesecond optical group is spaced apart from the first optical group byapproximately 27.5 mm.
 9. The digital camera of claim 8, wherein saidfirst optical group comprises a convexo-concave or meniscus lens. 10.The digital camera of claim 8, wherein said second optical group isspaced apart from the third optical group by approximately 12.1 mm. 11.The digital camera of claim 8, wherein the first optical group comprisesa negative focal length in a range between −5 mm and −20 mm.
 12. Thedigital camera of claim 8, wherein the third optical group furthercomprises a positive focal length of approximately 41.878 mm.
 13. Thedigital camera of claim 1, wherein at least one aspheric surfacecomprises an aspheric sag less than approximately 12 microns.
 14. Thedigital camera of claim 1, wherein at least one aspheric surfacecomprises an aspheric sag slope less than approximately 15 microns permillimeter.
 15. The digital camera of claim 1, comprising a singleaspheric lens element, which is the only aspheric lens element withinthe optical assembly, wherein lens elements other than the singleaspheric lens element comprise spherical or planar lens surfaces, orboth, each without significant aspheric departure.
 16. The digitalcamera of claim 1, comprising a single aspheric lens surface, which isthe only aspheric lens surface within the optical assembly, wherein lenssurfaces other than said aspheric lens surface comprise spherical orplanar lens surfaces, or both, each without significant asphericdeparture.
 17. The digital camera of claim 1, comprising only oneaspheric lens element.
 18. The digital camera of claim 1, comprisingonly one aspheric lens surface.
 19. The digital camera of claim 1,wherein a stray light irradiance ratio is below 1/10,000.
 20. Thedigital camera of claim 1, wherein a stray light power ratio is below1/100.
 21. The digital camera of claim 1, wherein axial chromaticaberration is less than 0.025 microns.
 22. The digital camera of claim21, wherein the axial chromatic aberration is defined by a ray trace at0.7 zonal in the stop, and across a spectral band between 465 nm to 650nm.